Abstract

When cultured in keratinocyte growth medium, mononuclear cytotrophoblast cells aggregate into multicellular colonies which then fuse to form multinucleated syncytiotrophoblast. In an attempt to characterize better the mechanism of human trophoblast differentiation and to obtain information about the role of the cytoskeleton, experiments were performed using cytoskeletal-disrupting drugs and primary cultures of cytotrophoblast cells from term placentae. Addition of colchicine 6 h after plating permitted aggregation but the cells did not form syncytiotrophoblast, as revealed by staining for desmosomes and nuclei. Staining with an anti-tubulin antibody showed that microtubules were present in untreated control cells but absent in colchicine-treated cultures. If colchicine was added 24 h after plating, the cells also failed to differentiate. When cells were exposed to colchicine for the first 24 h after plating and then cultured in the absence of the drug, differentiation proceeded normally. Cells exposed to colchicine for 48 h and then incubated in the absence of the drug failed to form syncytiotrophoblast. The results suggest that a decision to differentiate is made between 24 and 48 h after plating. The effects of colchicine were observed between 2.5 and 250 μ m . β-lumicolchicine blocked differentiation at 250 μ m but was ineffective at lower concentrations. Colchicine also inhibited HCG secretion in a dose-dependent manner; β-lumicolchicine only caused inhibition at 250 μ m . Staining with antitubulin antibody revealed that lumicolchicine-treated cells had intact microtubules. These results suggest a role for microtubules in trophoblast differentiation.